And from left to right, those icons are:

Tweetie, for all my Twittering needs.
Typinator, which is a typing auto-corrector. Makes it hard to type the word “Teh”.
Dropbox, which is an excellent network file-sync utility (with a good web interface).
Google Quick Search Box. I used to use Quicksilver. Alcor (the author of Quicksilver) started working at Google, and this is his project. It’s not a full replacement for Quicksilver yet, but it does the job for what I need.
Coversutra, which I use for controlling iTunes. It also does neat screen-pops when the song changes.
NetworkLocation automatically changes things like my screen brightness, default printer, proxy and security settings, screensaver, and background (among many others), whenever I connect to specific networks.
SlimBatteryMonitor, which I discovered through a MacWorld article. It’s just a battery charge meter, but it’s smaller than the Apple stock one.
Ejector, which lets me eject any mounted filesystem (network shares, CDs, flash drives, etc).
SynergyKM, which is a gui front-end for Synergy, a keyboard & mouse-sharing program.  Lets me control my linux workstation with the keyboard and mouse connected to my laptop.
Apple’s Bluetooth widget
Apple’s processor widget; it lets me disable one of my two processor cores, for better battery life.
Apple’s Monitor widget, for fast resolution changes.
SoundSource, a freebie from Rogue Amoeba. Lets me pick which input/output devices to use for the bleep-bloops.
Time Machine
Apple Airport status
I stopped using MenuCalendarClock; this is the built-in menubar clock from OS 10.5
Spotlight

Some day I may also do a similar inventory of the applications that live on the Dock. But I’d have to be even more bored than I am now, so don’t hold your breath!